Heat-sealable films are widely used in packaging applications for consumer items such as snacks, bakery over-wrapping, confectionery, etc. Heat-sealable films can be oriented polymeric films, such as BOPP films. In certain applications it is desirable to have a relatively low sealing initiation temperature (SIT), so that low temperature is necessary to initiate the sealing operation, permitting the packer to run at faster speeds or improving the seal integrity of the final pack. Heat-sealable BOPP plastic films are known from, for example, U.S. Pat. No. 8,431,234; U.S. Pat. No. 5,489,454; U.S. Pat. No. 4,996,096; and US Pub. 2012/0258307.
U.S. Pat. No. 8,431,234 discloses a BOPP film comprising a polyolefin base layer, and a heat-sealable matte resin layer consisting of 15 to 30 wt % of a metallocene-catalyzed propylene-butene copolymer (PBC) elastomer having a 20-40 wt % butene content. The film has at least a 60% haze measured in accordance with ASTM D1003. It is not possible to further lower the sealing initiation temperature (SIT) of this film because further increasing the PBC content to lower the SIT worsens the matte appearance (gloss increases and haze decreases). There are also issues with production continuity.